Stratifier belt assembly

ABSTRACT

A classifying conveyor belt assembly comprising an elongated base belt having a generally flat upper mounting surface, and a carrying cover mounted thereon. Said carrying cover has a plurality of alternating ridges and valleys formed in and extending transversely across same.

United States Patent Caldwell [451 Mar. 21, 1972 [54] STRATIFIER BELTASSEMBLY [72] inventor: William A. Caldwell, Olathe, Kans.

[73] Assignee: Phillips Petroleum Company [22] Filed: Dec. 10, 1969 [21]Appl. No.: 883,687

[52] U.S. Cl ..209/430, 209/485 [51] Int. Cl ..B03b 3/36 [58] Field ofSearch ..209/428433, 470, 209/485, 481, 506; 198/199 [56] ReferencesCited UNITED STATES PATENTS 783,769 2/1905 Wright ..l98/l99 X 2,414,993l/l94 7 Wiegand. ...209/485 X Morse ..209/43 3 1,050,991 1/1913 Ogle.209/433 860,500 1/1907 Tatman. ..209/433 3,403,781 10/1968 Drago.....209/506X FOREIGN PATENTS OR APPLICATIONS 98,861 8/1898 Germany..209/433 4,231 12/1892 Great Britain ..209/433 Primary ExaminerFrank W.Lutter Assistant Examiner Ralph J. Hill Attorney-Young and Quigg [57]ABSTRACT A classifying conveyor belt assembly comprising an elongated 1base belt having a generally flat upper mounting surface, and a carryingcover mounted thereon. Said carrying cover has a plurality ofalternating ridges and valleys formed in and extending transverselyacross same.

9 Claims, 6 Drawing Figures PAIENTEDMARZI I972 3,650,402

sum 1 OF 2 FIG. 2

FIG.

FIG. 3

INVENTOR.

W. A. CALDWELL J EU yam, w 97 A T TORNEKS PAIENTEDMARZ] I972 SEED-4G2SHEET 2 [1F 2 INVENTOR. W. A. CALDWELL BY 7 a ATTORNEYS WATER STRATIFIERBELT ASSEMBLY This invention relates to a conveyor belt assembly.

Conveyor belts having various classifying means built therein have beenemployed for classifying grain, sand, gravel, and the like. Theclassifying means is usually fabricated integrally into the structure ofthe belt. This type of construction has at least two seriousdisadvantages. First, the belt must be shut down periodically forcleaning. Secondly, when the integrally formed classifying means becomesworn, the entire belt must be discarded. It would be desirable to have aclassifying conveyor belt provided with a replaceable classifying meanswhich can be (a) readily cleaned while in operation and (b) readilyreplaced when worn, i.e., replaced without having to discard the entirebelt. The present invention provides such a classifying conveyor belt.

An object of this invention is to provide an improved classifyingconveyor belt. Another object of this invention is to provide aclassifying conveyor belt having a replaceable classifying means.Another object of this invention is to provide a classifying conveyorbelt which can be readily cleaned while in operation. Another object ofthis invention is to provide a classifying conveyor belt which isprovided with a removable classifying means formed of a semirigid solidplastic material. Other aspects, objects, and advantages of theinvention will be apparent to those skilled in the art in view of thisdisclosure.

Thus, according to the invention, there is provided a conveyor beltassembly comprising: an elongated base providing a generally flatmounting surface; a carrying cover mounted on said surface of said base;and a plurality of spaced apart, transversely extending, alternatingridges and valleys formed in said cover.

The carrying cover or replaceable classifying means in the belt of theinvention is preferably formed of a semirigid solid plastic material.Such materials which can be employed in the practice of the inventioninclude polyethylene, polypropylene, copolymers of ethylene or propylenewith another l-olefin, e.g., butene-l, polyvinylchloride,polytetrafluoroethylene, nylon, and the like. Particularly applicablefor use in the present invention are the polymers of ethylene,propylene, or other l-olefins prepared in accordance with the method ofU.S. Pat. No. 2,825,72l .l. P. Hogan et al. As used herein and in theclaims, unless otherwise specified, the word polymer is employedgenerically and includes both homopolymers and copolymers.

FIG. 1 is a view in elevation of a conveyor belt assembly in accordancewith the invention.

FIG. 2 and FIG. 3 are plan views of conveyor belt assemblies inaccordance with the invention.

FIG. 4 is a perspective view, partly in cross section, of anotherconveyor belt assembly in accordance with the inventron.

FIG. 5 is a diagrammatic view illustrating one assembly of apparatus inwhich the conveyor belt of the invention can be employed.

FIG. 6 is a cross-sectional view of the plastic hinge employed with theinvention.

Referring now to the drawings, wherein like reference numerals have beenemployed to denote like elements, the invention will be more fullyexplained. In FIG. 1 there is illustrated a conveyor belt assemblycomprising an elongated base belt 12 having a generally flat uppermounting surface 14. A carrying cover 16, preferably formed of asemirigid solid plastic material, is mounted on said surface 14 of saidbase belt 12. Any suitable means can be employed for mounting saidcarrying cover on said base belt. One presently preferred meanscomprises employing rivets 18, as at the overlapping ends of sections ofthe carrying cover, and also at intermediate points of the carryingcover, both as illustrated in said FIG. 1. Said carrying cover 16 hasformed therein a plurality of spaced apart, transversely extending,alternating ridges and valleys, as illustrated in FIG. 1.

Said alternating ridges and valleys can be formed in any suitable orconvenient manner. One presently preferred method of forming saidalternating ridges and valleys comprises forming a plurality of hingeswhich extend transversely across a sheet or web of a semirigid plasticmaterial, and then compressing said sheet or web longitudinally to causebending thereof and thereby form said valleys and ridges.

Such hinges can be formed merely by flexing of the semirigid plasticmaterial, which flexing causes molecular orientation in the line of theflexing. It is frequently preferred, however, to thin the sheet or webof plastic material along the proposed hinge line. This can be done byheating either the plastic material, or a bar or roller, to just belowthe softening point of the plastic material, and either pressing orrolling said plastic material to thin same along the line of theproposed hinge. The plastic material is then flexed along the line ofpressing or rolling. The hinge can alternately be formed by machining agroove in the plastic material with conventional wood or metal tools.Tool speed should be controlled so that excessive frictional heat is notgenerated in cutting the hinge line. Again, the hinge is formed byflexing the plastic material along the cut hinge line. Another method offorming the hinge comprises cold working the plastic material by passinga sheet thereof between two rollers so as to reduce the cross section ofthe plastic material along the desired hinge line. When the hinge isformed by flexing only, the flexing appears to reorient the plasticmaterial to produce a necked-down cross section which will be in therange of from 75 to percent of the original cross section. For example,a la-inch thick sheet will be necked down from both sides to leave across section approximately one-tenth of an inch in thickness with theneckeddown length being from one-eighth to one-fourth of an inch. Whenthe hinge is formed by prethinning the plastic material along a givenline and then flexing same, the hinge itself can be from 10 to 15 milsthick, and the hinge width can be between 30 and 60 mils. In suchinstances, the thickness will decrease slightly after the first flexingof the hinge due to neck-down" of the plastic. Thus, at least twosimilar methods are available for forming said hinges. The necked-downportion of the hinge is illustrated at 38 in FIG. 6. The width of thehinge is considered to be the distance between A and B.

The above methods of forming hinges in semirigid solid plastic materialsare known in the art and form no part of the instant invention. It isknown that hinges formed in various thermoplastic materials by themethods described above have exceptional flexlife characteristics.Polypropylene hinges, for example, formed by the methods describedabove, have withstood over a million flex cycles without failure.

The carrying cover in the belt assemblies of the invention can befabricated from sheets of semirigid solid plastic material having anysuitable thickness. It is presently preferred to use sheets having athickness within the range of about one-sixteenth to about one-fourthinch.

The number and size of the alternating ridges and valleys formed in thecarrying cover will depend upon the manner in which the belt assembly isemployed and the material being classified. While the invention is notlimited in this respect, generally speaking, the valleys will have adepth within the range of from about one-sixteenth to about 2 inchesmeasured vertically from the bottom of the valley, and the number ofridges will be within the range of from about four per inch to aboutthree per foot.

Preferably, the carrying cover will comprise a plurality of separatecover sheets connected to each other at adjoining ends thereof, e.g., asin FIG. I. Said cover sheets can be of any suitable length, dependingupon the overall length of the carrying cover. Said cover sheets willusually range from about 2 to about 6 feet in length. However, it iswithin the scope of the invention to form the carrying cover of onecover sheet joined at the ends thereof so as to provide a continuouscover for the base belt.

Said carrying cover can have any suitable width ranging from less thanthe width of the base belt as shown in FIG. 2, to greater than the widthof the base belt, as shown in FIG. 3. It is generally preferred thatsaid carrying cover have substantially the same as or slightly lesswidth than the width of the base belt. Said base belt can be formed ofany suitable conventional belting material, such as laminated rubber,canvas, or rubbercoated canvas, etc., Said base belt can have anysuitable width, depending upon the service it is employed in. Usuallysaid belt will range from 2 to 6 feet in width. Said base belt andcleaned. The surface of the plastic materials used in fabricating saidcarrying covers is virtually self-cleaning. Minerals,

, metals, and tailing materials associated therewith do not ad- 4 beabout the same height as the height of said flanges 20.

However, it is within the scope of the invention for the height of saidridges to be less than or greater than the height of said flanges 20. II

As indicated above, the classifying belts of the invention can beemployed in classifying and/or concentrating a wide variety ofmaterials. Generally speaking, any divided orparticulate material havinga specific gravity greater than one can be concentrated using the beltassemblies of the invention. Said belts of the invention areparticularly useful in classifying and/or concentrating mineral ores.The belts of the invention are especially suitable in the concentrationand recovery of gold. In such use said belts are suitable for therecovery of fine gold, coarse gold, or both together, and can be used ona feed stream as coarse as 10 mesh or as fine as 200 mesh, or finer. Thepulp density of the slurry feed to the belt will vary, depending uponthe type of previous milling treatment, but will usually run about 20percent solids.

FIG. illustrates diagrammatically one type of apparatus which can beemployed in the concentration of gold when using the belt assembly ofthe invention. In FIG. 5 a belt assembly is disposed around supportrollers 22 and 24, of which roller 22 is the drive roller and is drivenby means of motor 26 and the drive belt shown. The slope of said belt isusually fixed for a given machine and can range from about one-fourth toabout 3 inches per foot, depending upon the particular service in whichthe machine is being employed. The belt speed is adjustable and canrange from about 30 to 150 inches per minute. Belt speed is usuallyadjusted to slope and feed pulp density. In operation, a slurry or pulpof the mineral to be recovered is discharged from feed sole 28 onto thesurface of the belt 10. A stream of water is introduced onto said beltfrom conduit 30. The gold or other heavy mineral which settles on thebelt and is collected in the valleys therein is dragged up beyond theoutlet of feed sole 28 where it is contacted with the water from conduit30 which flows downslope along the belt. As the belt is rotated aroundroller 22, the material collected in the valleys of belt 10 is contactedwith a second stream of water from conduit 32 and washed onto thesurface of conveyor 34. Said conveyor 34 conveys the concentrated goldor other mineral to further processing steps. The tailings and otherlighter material which do not settle in the valleys on belt 10 arecarried down the surface of the belt by the downflowing stream of waterand deposited in a tailings box 36 which is disposed below and beyondroller 24. While not shown in the drawing, it is within the scope'of theinvention to employ the belt of the invention on machines similar tothat illustrated in FIG. 5 which are also provided with means forshakingthe belt.

A number of advantages are realized when employing the belt assembliesof the invention. One outstanding advantage is that the carrying coverof the belt assembly can be readily here to the surface of the carryingcover. All of said materials are easily removed by spraying with water.This is also advanta eous in that the heavy material which isconcentrated in the v leys of the carrying cover IS readily removedtherefrom without the necessity of a doctor blade. Another advantage isthe long life of the carrying cover. Said plasticmaterials areremarkably wear-resistant. Still another advantage is the low cost ofthe plastic material. Still another advantage is the ease of fabricationand replacement of the carrying covers, when such replacement doesinfrequently becomenecessary. When the carrying cover is fabricated froma plurality of cover sheets, still another advantage is obtained in thatindividual cover sheets can be replaced without having to replace theentire carrying cover. If the carrying cover should become damaged, itcan be repaired without difficulty by heat sealing,

fusion, why the use of epoxy adhesives.

While certain embodiments of the .invention have been described forillustrative purposes, the invention is not limited thereto. Variousother modifications of the invention will be apparent to those skilledin the art in view of this disclosure. Such modifications are within thespirit and scope of the disclosure.

I claim:

l. A classifier comprising: an inclined endless elongated base beltproviding a generally flat mounting surface; a semirigid carrying coverremovably mounted on said surface of said base; and a plurality ofspaced apart, transversely extending, self-sustaining alternating ridgesand valleys integrally formed in said cover when it is mounted on saidbase, means for driving said belt; and means for feeding material to beclassified onto said belt.

2. A belt according to claim 1 wherein said cover is formed of asemirigid solid plastic material.

3. A belt according to claim 2 wherein said plastic material is apolymer of ethylene or a polymer of propylene.

4. A belt according to claim 1 wherein: said cover comprises a semirigidsheet of solid plastic material having a plurality of spaced apartflexible hinges formed therein, said sheet being compressedlongitudinally to cause bending thereof at said hinges to form saidself-sustaining ridges and valleys when said sheet is mounted on andfixed to said base belt.

5. A conveyor belt according to claim 4 wherein: said cover comprises aplurality of cover sheets, connected to each other at adjoining endsthereof, and fixed to said base; and a plurality of said alternatingridges and valleys are formed in and extend transversely across each ofsaid cover sheets. I

6. A conveyor belt according to claim 5 wherein said plastic material ispolypropylene.

7. A classifier according to claim 1 wherein: said base belt is providedwith an upwardly extending flange at each side edge thereof; said covercomprises a plurality of cover sheets, connected to each other atadjoining ends thereof, and mounted on said surface of said base beltbetween said flanges; and a plurality of said alternating ridges andvalleys are formed in and extend transversely across each of said coversheets.

8. A classifier according to claim 7 wherein: said cover sheets areformed from a semirigid sheet of solid plastic material; saidalternating ridges and valleys comprise a plurality of spaced apartflexible integral hinges formed in each said cover sheet; and each saidcover sheet is compressed longitudinally to cause bending thereof atsaid hinges and form said ridges and valleys.

9. A classifier according to claim 8 wherein said plastic material ispolypropylene.

1. A classifier comprising: an inclined endless elongated base beltproviding a generally flat mounting surface; a semirigid carrying coverremovably mounted on said surface of said base; and a plurality ofspaced apart, transversely extending, selfsustaining alternating ridgesand valleys integrally formed in said cover when it is mounted on saidbase, means for driving said belt; and means for feeding material to beclassified onto said belt.
 2. A belt according to claim 1 wherein saidcover is formed of a semirigid solid plastic material.
 3. A beltaccording to claim 2 wherein said plastic material is a polymer ofethylene or a polymer of propylene.
 4. A belt according to claim 1wherein: said cover comprises a semirigid sheet of solid plasticmaterial having a plurality of spaced apart flexible hinges formedtherein, said sheet being compressed longitudinally to cause bendingthereof at said hinges to form said self-sustaining rIdges and valleyswhen said sheet is mounted on and fixed to said base belt.
 5. A conveyorbelt according to claim 4 wherein: said cover comprises a plurality ofcover sheets, connected to each other at adjoining ends thereof, andfixed to said base; and a plurality of said alternating ridges andvalleys are formed in and extend transversely across each of said coversheets.
 6. A conveyor belt according to claim 5 wherein said plasticmaterial is polypropylene.
 7. A classifier according to claim 1 wherein:said base belt is provided with an upwardly extending flange at eachside edge thereof; said cover comprises a plurality of cover sheets,connected to each other at adjoining ends thereof, and mounted on saidsurface of said base belt between said flanges; and a plurality of saidalternating ridges and valleys are formed in and extend transverselyacross each of said cover sheets.
 8. A classifier according to claim 7wherein: said cover sheets are formed from a semirigid sheet of solidplastic material; said alternating ridges and valleys comprise aplurality of spaced apart flexible integral hinges formed in each saidcover sheet; and each said cover sheet is compressed longitudinally tocause bending thereof at said hinges and form said ridges and valleys.9. A classifier according to claim 8 wherein said plastic material ispolypropylene.